The disclosure relates to the wing design for aircrafts driven by propellers or other rotors in tractor configuration and a method for reducing the induced drag and the total drag and/or any other such aerodynamic parameters of interest that is affected as a result of at least one propeller slipstream flowing onto a wing.
In a propeller-driven aircraft there is an aerodynamic interaction between the propeller slipstream and the wing. This is of great significance in particular if the propeller(s) is/are situated in front of the wing, for example a turboprop aircraft in tractor configuration. During operation propellers not only produce a thrust but also accelerates and imparts a swirl to the flow downstream of the propeller. This results in a propeller air flow (hereinafter also referred to as a “propeller slipstream”) that impinges in a helical or spiral shape on the wing surface that is situated behind it. Depending on the direction of rotation of the respective propeller there is an increase or reduction in the local angle of attack on the wing. Consequently there is a corresponding deformation of the lift distribution on the wing as a result of which, other things being the same, there is an increase in the induced drag of the wing.
Since the early 1990's there has been a decline in the usage of turboprops because of availability of cheap oil. At that time jets were preferred as they were affordable, faster and quieter. However, owing to climate change concerns and connectivity demands, turboprops are now once again becoming more attractive. Hence, there is a need to explore new technologies associated with turboprops and other rotor driven aircraft and optimize them for better performance.
The existing technologies currently associated with propeller-driven aircraft do not take adequate account of the potential to exploit the effects of the propeller slipstream to design a better wing. Improving aerodynamic efficiency has become increasingly important in recent years due to uncertain fuel prices and concerns about climate change. This is because, the propeller and rotor-driven aircraft in particular turboprops, are inherently more energy efficient than turbojets.
The disclosure addresses the problems due to the propeller slipstream by extending lifting line theory to include propeller effects and coupling it to an optimizer, which generates novel wing designs which offer better aerodynamic performance such as lower drag by optimizing the chord distributions for prescribed twist distributions or other constraints.